Climate-smart canola: quantifying soil- and fertilizer-derived nitrogen sources and greenhouse gas emissions
Term: 3 years, ending in June 2025
Status: Complete
Researchers: Melissa Arcand, Kate Congreves & Rachelle McCannell, University of Saskatchewan; Sally Vail, Agriculture and Agri-Food Canada
SaskCanola Investment: $62,038
Total Project Cost: $296, 152
Funding Partners: ACPC, MCGA, Western Grains Research Foundation
Objectives
The goal of this project was to bring together physiological and agronomic understanding of canola nitrogen use efficiency (NUE) with an understanding of soil contributions to canola nitrogen (N) fertility using 15N stable isotope tracing to paint a more complete picture of canola NUE. Researchers built on previous and current NUE research using a diverse set of canola genotypes that includes hybrids, historical open-pollinated cultivars, and breeding lines through AAFC’s canola breeding program to understand the range in NUE and the mechanisms underpinning NUE to identify breeding targets.
Project Description
This study evaluated NUE and environmental losses across a diverse set of canola lines, that included parental breeding lines, experimental hybrids, and a commercial hybrid line. The study was conducted over two years under dryland conditions at Saskatoon (2022, 2023) and one year under irrigated conditions at Outlook (2022) for a total of three site-years. 15N isotope tracing was used to differentiate contributions of fertilizer vs. soil N to canola N uptake to better understand crop N sources as well as to examine fertilizer N recovery in the plant and soil system to better understand N losses. Greenhouse gases were sampled and PRS® probes evaluated soil inorganic N supply rates to evaluate soil N dynamics and environmental impacts.
Grower Benefits
This study highlights the influence of environmental stress—particularly drought and high temperatures—on canola productivity and NUE. Despite applying 100 kg N ha⁻¹, fertilizer recovery was low, soil N contributions to plant N uptake were dominant, and over half of the applied nitrogen was unaccounted for by the end of the growing season. These findings suggest that under moisture-limited conditions, environmental constraints, rather than N availability, were the primary factors limiting yield and NUE, and likely overshadowed genetic differences among canola lines. While some experimental hybrids showed promise, biomass accumulation, not fertilizer uptake, was the key driver of NUE. The limited crop response to fertilizer N under the moisture-limited conditions experienced in the two growing seasons indicates that yield potential was not high enough to fully utilize available N. Although soil-derived N sources, via N mineralization, had a high contribution to crop N supply and are important to consider in the fate of N in the soil-plant system, this should not be interpreted as a sustainable substitute for fertilization. Increased water availability under more favourable conditions is expected to increase N fertilizer responsiveness with greater potential to differentiate NUE among canola lines. Future research should focus on identifying and breeding canola lines that maintain NUE and yield under environmental stress. Additionally, exploring water use efficiency, alternative fertilizer formulations, placement strategies, and soil health practices may help improve nitrogen retention and crop uptake.